The present invention relates to an image filing system for storing image data such as medical image data retrievably in a storage medium, and more particularly to an image filing system which has retrieval data containing link information between image data representative of a plurality of images, the image filing system allowing the image data to be selected according to the link information and to be transmitted to an output device such as a display unit or a printer.
Many medical images, i.e., images containing medical information of patients' bodies, are widely used for medical treatment and research activities in medical and clinical organizations such as hospitals. Most of such medical images are radiation images, but more and more CT (computer tomography) images and MRI (magnetic resonance imaging) images recently as medical images. These medical images are stored as records of patients' conditions and accessed for diagnosis, when necessary. The medical images are legally required to be kept for a certain period of time. As a result, the number of medical images stored in medical and clinical organizations grows day by day.
Heretofore, medical images have been stored as hard copies. It has been a burdensome task for medical and clinical organizations to have a sufficient storage space for medical images, to keep stored medical images in order, and to access and retrieve desired images. Recently, there has been proposed an electronic image filing system for storing medical images as image data retrievably in a mass storage device such as an optical disk, as disclosed in Japanese Laid-Open Patent Publications Nos. 63(1988)-18436 and 63(1988)-6664. The electronic image filing system reduces the space and labor needed to store medical images, and allows stored images to be accessed and retrieved easily and quickly.
The electronic image filing system has a data base including stored image data and retrieval data, such as patients' information and imaging information, corresponding to the stored image data. Desired image data can be accessed and retrieved according to corresponding retrieval data. The image data are usually stored in an optical disk which has a very large storage capacity because even a single image contains a great amount of image data. However, since the amount of retrieval data is relatively small as compared with the image data, the retrieval data are usually stored in a high-speed storage device such as a magnetic disk, so that any desired image data can quickly be retrieved according to corresponding retrieval data.
Generally, many different medical images are taken of different body regions at different times or dates under different imaging conditions for one individual or patient. In order to successively display related ones of these medical images for comparison, an electronic image filing system should efficiently retrieve and output those related medical images. In view of such a demand for high-speed retrieval and output capability, there has been proposed an image filing system which transfers image data from an optical disk to a magnetic disk or the like that can be accessed at high speed, and then reads an image from the magnetic disk for output. For example, Japanese Laid-Open Patent Publication No. 62(1987)-271178 discloses an image filing system in which a particular image is retrieved and outputted and a plurality of images that precede and follow the particular image are also transferred to a magnetic disk or the like.
The disclosed image filing system is effective in use if related images are successively recorded, but ineffective if related images are recorded at random. In large-scale hospitals or other medical and clinical organizations, various body regions of several hundred patients are imaged and stored in an optical disk in one day. It is very rare for related images of a particular patient to be recorded in successive storage locations in the optical disk. Therefore, related images of a particular patient cannot usually be retrieved at high speed by the above disclosed image filing system.